1. Field of the Invention
This invention relates to a package connector apparatus, and more particularly to a connector apparatus for electrically connecting a package including an electric circuit mounted on a printed circuit board to an external circuit.
2. Description of the Related Art
Conventional package connector apparatus are popularly formed as package connector apparatus of the through-hole dip type. Exemplary construction one of such conventional package connector apparatus is shown in FIG. 6. Referring to FIG. 6, a connector body 1 is secured to the front surface, that is, an upper face, at an end portion of a printed circuit board 2. A plurality of contacts or pins 4 are provided in for example, four, horizontal rows and extend horizontally from a vertical side face 3 of the connector body 1. The contacts 4 are individually bent into an L-shape such that they extend downwardly from intermediate portions thereof. The L-shapes of the contacts 4 are different from each other that, in each vertical column, each contact 4 has a smaller L-shape than an adjacent contact 4 above it and is included in the L-shape of the adjacent contact 4. The other end portions of the contacts 4, which extend downwardly, extend through corresponding through-holes 5 perforated in the printed circuit board 2 and downwardly below the rear surface, that is, a lower face, of the printed circuit board 2. Each of the contacts 4 is soldered, at a portion thereof in the corresponding through-hole 5, to a wiring pattern (not shown) on the printed circuit board 2. A circuit part 6 is mounted on the printed circuit board 2. Another connector 8 is mounted on another printed circuit board 7 of another package to which the package including the connector body 1 is to be connected.
The package connector apparatus of the throughhole dip type of FIG. 6 has a problem. In particular, since electromagnetic waves are radiated from each contact 4 when the frequency of a signal passing the contact 4 is high, the characteristic impedance of the contact 4 varies at a portion thereof which extends downwardly from the lower face of the printed circuit board 2 to cause a discontinuous point of the characteristic impedance, which deteriorates the signal transfer characteristic of the contact 4.
The problem can be solved if the package connector apparatus is constructed as a package connector apparatus of the SMT (Surface Mount Technology) type which eliminates through-holes. Thus, it seems a possible solution to employ such a structure as shown In FIG. 7. Referring to FIG. 7, a plurality of contacts 4 are provided in a plurality-of horizontal rows in upper and lower areas of a vertical side face of a connector body 1, and the contacts 4 in the upper area of the connector body 1 extend along an upper face 3 of a printed circuit board 2 and are connected, at the other ends thereof, to wiring patterns (not shown) 0n the upper face of the printed circuit board 2 while the contacts 4 In the lower area of the connector body 1 extend along a lower face of the printed circuit board 2 and are connected, at the other ends thereof, to wiring patterns (not shown) on the lower face of the printed circuit board 2. The connector body is supported so that an intermediate portion between the upper and lower areas thereof, that is, the center thereof in the vertical direction, is opposed to and not displaced from the printed circuit board 2.
With the package connector apparatus of the SMT type, since the connector body 1 is supported such that the center thereof in the vertical direction is opposed to the printed circuit board 2, the connector body 1 extends both upwardly and downwardly equally above and below the upper and lower faces of the printed circuit board 1, respectively. Consequently, the position of the connector body 1 with respect to the printed circuit 2 is different from that of the connector body 1 of the package connector apparatus of the through-hole dip type shown In FIG. 6. Consequently, SMT type package connector has no compatibility with the through-hole dip type which are used very popularly. The package connector apparatus of the two types cannot be employed commonly in the same appliance, which is inconvenient. Further, since the connector body 1 extends both upwardly and downwardly by a length equal to substantially one half the height thereof above and below the upper and lower faces of the printed circuit board 2, when a plurality or package are to be arranged in an overlapping relationship parallel to each other, where all of the packages are of the SMT type or some of the packages are of the SMT type and the remaining packages are of the through-hole dip type, in order to prevent each adjacent packages from interfering with each other, a greater distance is required between adjacent packages than that which is required between adjacent packages when all of the packages are of the through-hole dip type. In order to restrict the distance to a conventional level, circuit parts to be mounted on the printed circuit board 2 must be reduced in size as much.